Iraqi military officials say government forces secured a contested area south of the country's largest oil refinery on April 17 as part of ongoing operations against Islamic State militants in northern Iraq.

General Ayad al-Lahabi said government troops in Salahuddin Province, backed by U.S.-led coalition air strikes and Shi'ite and Sunni militia, regained control of the towns of Al-Malha and Al-Mazraah, about three kilometers south of the Baiji oil refinery.

Lahabi said about 160 Islamic State militants were killed in the battle for control of the towns.

He said Iraqi forces are now fighting to break the siege by IS militants who have been surrounding the Baiji refinery, which remains under the control of government troops.

Iraqi forces on April 2 recaptured the city of Tikrit further south of the refinery.

In Ramadi, the capital of Iraq's western province of Anbar, IS militants took control of a number of areas in the central part of the city.

Security forces, however, managed to prevent them from capturing the big State Mosque in the city center after heavy fighting.

Ramadi residents have been leaving the city in droves.

IS militants launched an offensive on Ramadi on April 15 and have advanced within two kilometers of the city's east side.

Meanwhile, the United States and its allies launched 21 air strikes targeting Islamic State militants in Iraq and Syria over the past 24 hours, the Combined Joint Task Force leading the operations said in a statement April 17.

The coalition staged 13 of the strikes across Iraq, including two near Ramadi that, according to the task force, hit a unit of IS fighters and destroyed a heavy machine gun, a vehicle, and an excavator.

Other strikes hit near Mosul, Fallujah and Sinjar, among other cities.

In Syria, eight strikes staged near Al-Hasaka and Kobani hit five units of Islamic State militants and destroyed various fighting positions and vehicles, the statement said.